Global hydrology 2015: State, trends, and directions

Global hydrology has come a long way since the first introduction of the primitive land surface model of Manabe (1969) and the declaration of the Emergence of Global Hydrology by Eagleson (1986). Hydrological submodels of varying complexity are now part of global climate models, of models calculating global terrestrial carbon sequestration, of earth system models, and even of integrated assessment models. This paper reviews the current state of global hydrological modeling, discusses past and recent developments, and extrapolates these to future challenges and directions. First, established domains of global hydrological model applications are discussed, in terms of societal and science questions posed, the type of models developed, and recent advances therein. Next, a genealogy of global hydrological models is given. After reviewing recent efforts to connect model components from different domains, new domains are identified where global hydrology is now starting to become an integral part of the analyses. Finally, inspired by these new domains of application, persistent and emerging challenges are identified as well as the directions global hydrology is likely to take in the coming decade and beyond.